pinholes

1. Defects in paper appearing as small punctures
which are caused by fine particles of alum, clay,
sand, etc., being crushed and falling out 1. when
the paper is calendered. Very hard grit may also
be imbedded in the steel rolls of the calender
itself and produce pinholes at each revolution. 2.
Large pores in a thin paper where fine fibrous
material or fillers fail to fill the voids between
larger fibers. 3. Minute almost imperceptible pits
in the surface of a coated paper. 4. Very small
transparent dots which appear in a lithographic
paper after development and which, unless covered
by an opaque medium, may affect printing. 5. Very
small holes in a fabric. 6. Small punctures found
in the untrimmed margins of printed books and
caused by the pins attached to the tympan used in
obtaining perfect registration of inner and outer
forms. They are usually not seen in folios because
they are in the fold, unless, as in some very
early books, there are two pairs of pins, in which
case they will be seen in the center of the top
and bottom margins of each leaf. In quartos they
will be in or very near the crease of the head BOLT , and evidence
of them can often be found even if the bolt has
been opened. In octavos they appear in the lower
fore edge margins of the first four or last four
leaves of each GATHERING (2) and are
also discernible even if the bolt has been opened.
See also: POINT
(5, 6). (17 , 341 )